The Central Biochemistry Laboratory (CBL) serves the subjects and investigators of the continuing Prospective Study of Chronic Kidney Disease in Children (CKiD). The CBL provides participating clinical sites with protocols, kits, reagents, supplies, and transportation required for performing iohexol-based glomerular filtration rate (GFR) studies and collecting blood and urine for analysis at URMC and other laboratories. Blood analytes include electrolytes, BUN, creatinine, glucose, calcium, phosphorus, albumin, uric acid, lipid screen, hsCRP, intact PTH, and cystatin C. Urine analytes include creatinine, protein, and microalbumin. The CBL has determined optimal conditions for transporting these analytes, and provides ambient shippers for each visit and quarterly dry ice shippers for frozen specimens. The CBL also provides the kits and instructions for collection and shipment of blood, plasma, sera, urine, hair, and nail samples to NIH repositories. Biochemical data from each CKiD visit are reviewed and entered into Nephron, the CKiD data base. The CBL provides training at annual CKID meetings and is readily available to provide information, instruction, and support during CKiD visits, as needed by the site coordinators. The CBL contributes expertise in performing biochemical assays and clinical interpretation of the results. The CBL collaborates regularly with the Data Coordinating Center (DCC) to optimize GFR studies and to construct GFR estimating equations used during odd number visits at which no iohexol study is performed, maintain the Manual of Procedures, assure the quality control of all assays, and provide continuity of biochemical assays through changes in instrumentation. The CBL participates in all Steering Committee meetings and conference calls and collaborates with investigators in the generation of abstracts, presentations, and manuscripts, which further document the success of the CKiD study. The aims of the CBL center on continuing to provide accurate, precise, and efficient measures of iohexol-based GFR and biochemical measurements of general kidney health. A pilot study to determine if fingerprick samples can replace serum collections for the iohexol GFR continues during this cycle. We plan to develop better GFR estimating equations, particularly for the children of Cohort 2, who have higher levels of GFR than those of Cohort 1. The CBL has submitted concept sheets to further determine if hyperuricemia predicts renal progression or hypertension, if microalbuminuria is a better predictor of renal progression than urinary protein, and to examine beta trace protein to determine if it is useful in predicting GFR. Finally, the CBL will continue to provide to the participating sites subject- and visit specific- laboratory kits for the collection, handling, and transport of samples, as well as receive, process, and analyze these samples on a daily basis, and provide timely data entry into Nephron. The long term goal is to better characterize the CKiD population biochemically, maintain the integrity of the data, and to optimize the collection of specimens in a manner that maintains recruitment and retention of CKiD subjects.